Conventional door hinges suffer from a number of well-known problems. They are difficult to install because vertical and angular positioning tolerances on the hinge plate are small. This makes it difficult to mount the hinges on the frame and the closure member such as a door and be sure that they are properly aligned relative to each other in the field when the closure is being mounted on the frame. Hence it is common practice to make pre-hung door assemblies in a factory using jigs or the like wherein alignment is performed under controlled assembly conditions and for the user to purchase such factory made pre-hung doors assemblies. Obviously, such assemblies are comparatively expensive.
It is also necessary to accurately align the cooperating hinge plates prior to putting the hinge pins into place which makes mounting the closure more difficult and time-consuming.
In use a conventional door hinge does not easily accommodate significant differential warping of the door and frame that occurs in may cases e.g. due to settling or humidity changes and thus results in "squeaky" hinges. Also conventional hinges are not mounted with the hinge pins on the outside to allow outward opening as this poses a security problem as the hinge pins are exposed and need only be removed to obtain entry.
A number of different hinge structures have been suggested and patented that attempt to overcome some of these difficulties including accommodating differential warping or some relative displacement of the frame and door or closure member.
Attention is directed to U.S. Pat. No. 4,370,829 issued Feb. 1, 1983 to Wagner, U.S. Pat. No. 4,864,690 issued Sep. 12, 1989 to Chen, U.S. Pat. No. 5,150,500 issued Sep. 29, 1992 to Bisbing, U.S. Pat. No. 5,249,334 issued Oct. 5, 1993 to Horberg et al. and U.S. Pat. No. 5,263,227 issued Nov. 23, 1993 to Hrbek et al. In all of these patented structures, at least one of the hinges is formed with a spherical mounting to accommodate relative angular displacement of the frame to and door. Most of these hinges are relatively complicated and do not permit easy assembly and some require bolting the hinge parts together.
Canadian patent 993612 issued Jul. 27, 1976 to Meertin et al. (see also U.S. Pat. No. 3,832,754 issued Sep. 3, 1974 to Meertin et al.) discloses a structure in which a supporting hinge uses a ball bearing or on a needle type bearing received in a shaped bearing (shallow socket) of the hinged member and an alignment hinge uses a substantially right cylindrical bearing enclosing the spherical member. This hinge structure accommodates significant misalignment, but is unstable as the supporting hinge may be easily dislodged laterally, for example, by simply overcoming the weight of the hinge member and slightly raising the one supporting hinge members to displace the ball or needle from its seat thereby freeing the member for lateral displacement and misalignment.